1. Field of the Invention
This invention relates to a labeling machine for automatically glueing labels to containers such as bottles and cans and particularly to a roll labeler or labeling machine of the type in which a label sheet in the form of a roll is unwound, cut and glued to a container. More specifically, the present invention relates to a roll labeler in which a label sheet unwound from a roll is intermittently supplied to a cutting section where the label sheet is cut into a desired size, and the label thus cut is glued to a container which is being transported by a container transporting mechanism.
2. Description of the Prior Art
In some prior art roll labelers, a label sheet unwound from a roll is intermittently supplied to a cutting section by a feeding mechanism, where a label having a desired shape and size is cut from the label sheet. In such roll labelers, typically, the label sheet is provided with registration marks which are detected to produce detection signals while the label sheet is being supplied by the feeding mechanism. In response to each of such detection signals, there is generated a feed stop command signal which causes the feeding mechanism to stop supplying the label sheet.
In the above-described prior art roll labelers, however, a time interval from the generation of a stop feed command signal to the actual stoppage of the label sheet is fixed. Accordingly, if the transportation speed for transporting containers to be labeled along a predetermined transportation path varies, the feeding speed of the label sheet also varies in response thereto, which, in turn, causes the supplied amount, or length, of label sheet to vary during the time interval between the generation of the feed stop command signal and the stoppage of supply of the label sheet. As a result, for example, during a start-up mode in which the operational speed gradually changes from a low level to a high level, the timing to generate a feed stop command signal in response to the direction signal must be suitably adjusted in association with the transporting speed of containers and thus the operational speed of the roll labeler.
For this reason, in the prior art roll labelers, typically, the operational speed of the roll labeler is monitored and the above-mentioned timing is suitably adjusted in accordance with the level of the operational speed of the roll labeler. With such a structure, however, it is necessary to adjust such timing in a continuous manner in accordance with changes in the operational speed, and optimum adjustment of such timing over the entire range of operational speed is not always easy.